LeetCode - Encode And Decode TinyURL

最新推荐文章于 2025-05-23 02:45:00 发布

RojerAlone

最新推荐文章于 2025-05-23 02:45:00 发布

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分类专栏： LeetCode 文章标签： leetcode

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本文介绍了一种URL缩短服务的设计方案，通过双向映射的方式确保长URL与短URL之间的唯一对应关系。具体实现中，使用了随机生成字符串的方法来创建短URL，并通过哈希表进行存储。

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题目

TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/problems/design-tinyurl and it returns a short URL such as http://tinyurl.com/4e9iAk.

Design the encode and decode methods for the TinyURL service. There is no restriction on how your encode/decode algorithm should work. You just need to ensure that a URL can be encoded to a tiny URL and the tiny URL can be decoded to the original URL.

　　输入一个长的URL，输出一个短的URL，并且每次输入输出要对应。

思路

　　将长URL和短URL在map中双向映射，生成短URL时随机选取6个字符，如果有重复的，就再次生成。

代码

public class EncodeAndDecodeTinyURL {

    private static final String CODE = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

    private Map<String, String> map = new HashMap<>();

    // Encodes a URL to a shortened URL.
    public String encode(String longUrl) {
        String res = map.get(longUrl);
        if (res != null) {
            return res;
        }
        res = "http://tinyurl.com/";
        Random random = new Random();
        for (int i = 0; i < 6; i++) {
            res += CODE.charAt(random.nextInt(62));
        }
        // 有重复的就再次生成
        while (map.containsKey(res)) {
            for (int i = 0; i < 6; i++) {
                res += CODE.charAt(random.nextInt(62));
            }
        }
        map.put(longUrl, res);
        map.put(res, longUrl);
        return res;
    }

    // Decodes a shortened URL to its original URL.
    public String decode(String shortUrl) {
        return map.get(shortUrl);
    }

}